SF Cyclotouring

Ride reports and other ramblings from a San Francisco cyclist.

7/10/2008

My Next LED Bike Headlight Project

Not that I don't have too much to do already, but I've been irrationally obsessing over LED bike lights lately. I say "irrationally" because it's mid-summer where I live and the daylight lasts a good long while, making bike lights mostly unnecessary for me right now. I know that will change soon, though. (I should also be focusing on work, and at least a dozen other things, but I digress...)



Part of my light-lust is being fueled by the recent introductions of a couple of commercial dynohub-powered lights, namely the Schmidt Edelux and the Supernova E3. Both of these are attractive lights, and are reputed to be very bright. However, they represent one problem inherent in current LED-based bicycle lights: the fact that technological improvements often happen faster than product development life cycles.


What do I mean by this? Both of the lights above are based on LEDs that were state-of-the-art six months to a year ago. I don't know for certain, but I'd guess that both lights are based on Cree 7090 XR-E LEDs. The efficiency of these LEDs, ranked by their bin codes, improves constantly -- caught up in a sort-of arms race with other LED manufacturers (Luxeon and SSC), Cree seems to produce ever-higher bin codes every few months. Since it takes many months (to a year or more) to imagine, develop, prototype, manufacture, and ship a commercial product, what this ultimately means is that the commercial bike-lights you can buy today aren't using the best components available now!


Additionally, the Edelux and E3 are both single-emitter (one LED) lights. While these designs may be brighter than their halogen-incandescent predecessors, many folks are still choosing to run multiple lights on their bikes for increased output. At over US$100 each, these lights aren't cheap, and mounting two is even more costly. Why duplicate things -- I don't see the need for the extra lamp housing, wiring, switch, etc. required by the second light unit? Why not simply make multi-emitter dynohub-powered lights, with two (or more) LEDs in a single casing? This adds only the minimal cost and weight of the extra LEDs, and is the option most DIY projects take.


Furthermore, in addition to advancements in LED efficiency, new designs are becoming available: multi-core LEDs are the new thing. These emitters basically combine four diodes into a single device with the same footprint as a single-emitter LED (analogy: think four filaments in a single incandescent bulb), quadrupling the light output!


So, my next bike light project will involve getting a dynohub front wheel, and building either a three or four LED light head or a lamp based on a quad-core LED. I'm not sure when I'll get started on this, but the results should be brighter than what I can buy "off the shelf" right now! Plus, I will no longer have to futz with the batteries my other light requires...

5 Comments:

Blogger Tom said...

Very Cool. I'm on the same track, just getting wheel built -- would love to see what you end up with!

6:07 PM  
Blogger Alan said...

The LED is only half the story with the E-Delux - it uses the B&M IQ Fly reflector. Cateye's "Reverse Offset Lens" lights claim similar benefits from their reflector design.
A multi-emitter design with comparable focusing ability will need multiple specially designed reflectors. A multi-core design will be even harder to focus.
It depends on the sort of riding you want it for though - for some applications just splashing a lot of light around is fine.

1:20 AM  
Blogger dolan said...

Neat stuff. I've been pretty happy with my dynohub/IQ fly combo, but nice to know brighter is always around the corner.

8:30 PM  
Blogger elybike said...

I just picked up an E3 for a friend, from Harris Cyclery in West Newton. The overall design is awesome, but it was almost $200. He runs a Schmidt with 2 lights up front.
I use a shimano dyno with a shimano light, mounted to the fork with a Minoura mount.Hope to try some of the SF brevet series this year....

5:53 AM  
Blogger amabele said...

i appreciate your efforts at looking critically at these lights. i think you may be missing a critical player in the supernova. The critical feature that distinguishes this light is the ability to upgrade it as led tech advances:
http://sheldonbrown.com/harris/lighting/supernova.html

an independent test of the leading lights:
http://www.velociped.ch/docs/Dynamo-Scheinwerfervergleich_2008.pdf

their website shows the well developed mounting options:
http://www.nova-factory.com/store_en.htm

review by the woman who convinced harris cyclery to carry this light:
http://www.blayleys.com/articles/lights/page3.htm

another competitor you might appreciate:
http://www.solidlights.co.uk/products/1203d.php

jorge

ps i appreciate your grounded non-hype review of the kogswell and i TOTALLY can identify with the procrastinating on bike projects...i don't understand it either

10:26 PM  

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